The present invention relates to a solid catalyst for polymerizing an olefin. Particularly, the present invention relates to a solid catalyst which can polymerize an olefin at a high polymerizing activity and produce a high molecular weight olefin polymer even when aluminoxane content of the catalyst is reduced. More particularly, the present invention relates to a solid catalyst for polymerizing an olefin which can produce a spherical olefin polymer having a good particle size distribution as well as excellent bulk density when slurry polymerization or gas-phase polymerization, particularly gas-phase polymerization is carried out. The present invention further relates to a solid catalyst which can polymerize an olefin at a high polymerizing activity and produce an olefin polymer having a narrow molecular-weight distribution or an olefin copolymer having a narrow composition distribution as well as the molecular-weight distribution when applied to a copolymerization of two or more olefins.
.alpha.-olefin polymers, particularly ethylene polymer and ethylene-.alpha.-olefin copolymer have generally been prepared by a known process wherein ethylene is polymerized, or ethylene and an .alpha.-olefin are copolymerized under the presence of a titanium-based catalyst comprising a titanium compound and an organoaluminum compound or a vanadium-based catalyst comprising a vanadium compound and an organoaluminum compound.
A new series of Ziegler catalysts comprising a zirconium compound and an aluminoxane have also been recently proposed for polymerization of an olefin.
Japanese Patent Application Kokai No. 58-19309 describes a process for polymerizing ethylene and at least one C.sub.3-12 .alpha.-olefin at a temperature of from -50.degree. to 200.degree. C. under the presence of a catalyst comprising a transition metal-containing compound represented by the formula: EQU (cyclopentadienyl).sub.2 MeRHal
wherein R is selected from cyclopentadienyl, C.sub.1-8 alkyl, and halogen, Me is a transition metal, and Hal is a halogen,
a linear aluminoxane represented by the formula: EQU Al.sub.2 OR.sub.4 (Al(R)--O).sub.n
wherein R is methyl or ethyl, and n is a number of 4 to 20, and
a cyclic aluminoxane represented by the formula: ##STR1## wherein R and n are as defined above. There is also described that ethylene should be polymerized under the presence of a small amount, that is, up to 10% by weight of an .alpha.-olefin having a somewhat longer chain or a mixture thereof to adjust a density of the resulting polyethylene.
Japanese Patent Application Kokai No. 59-95292 describes processes for preparing a linear aluminoxane represented by the formula: ##STR2## wherein n is a number of 2 to 40 and R is a C.sub.1-8 alkyl, and a cyclic aluminoxane represented by the formula: ##STR3## wherein n and R are as described above. There is also disclosed that at least 25 million grams of polyethylene may be produced per 1 g of transition metal per hour when an olefin is polymerized under the presence of a mixture of, for example, methylaluminoxane prepared as described above and a bis(cyclopentadienyl) compound containing titanium or zirconium.
Japanese Patent Application Kokai 60-35005 discloses a process for preparing an olefin-polymerization catalyst comprising effecting a reaction between a magnesium compound and an aluminoxane compound represented by the formula: ##STR4## wherein R.sup.1 is a C.sub.1-10 alkyl radical, and R.sup.0 may represent R.sup.1 or, taken together, form --O--; chlorinating the reaction product; and treating the product with Ti, V, Zr, or Cr-containing compound to produce an olefin-polymerizing catalyst. There is also disclosed that said catalyst is particularly preferable for copolymerizing ethylene with a C.sub.3-12 .alpha.-olefin.
Japanese Patent Application Kokai No. 60-35006 discloses a catalyst system for polymers blended in a reactor which comprises a combination of (a) a mono-, di- or tri-cyclopentadienyl compound of at least two different transition metals, or a derivative thereof, and (b) an alumoxane (aluminoxane). Example 1 of this application discloses that a polyethylene having a number average molecular weight of 15,300, a weight average molecular weight of 36,400, and propylene content of 3.4% may be prepared by polymerizing ethylene and propylene by using bis(pentamethylcyclopentadietnyl)zirconium dimethyl and an alumoxane as catalyst. Example 2 discloses that a blend of polyethylene and ethylene-propylene copolymer having a number average molecular weight of 2,000, a weight average molecular weight of 8,300, and propylene content of 7.1 mol % comprising toluene-soluble portion having a number average molecular weight of 2,200, a weight average molecular weight of 11,900, and propylene content of 30 mol % and toluene-insoluble portion having a number average molecular weight of 3,000, a weight average molecular weight of 7,400, and propylene content of 4.8 mol % may be prepared by polymerizing ethylene and propylene by using bis(pentamethylcyclopentadienyl)zirconium dichloride, bis(methylcyclopentadienyl)zirconium dichloride, and an alumoxane as catalyst. Example 3 discloses a blend of LLDPE and ethylene-propylene copolymer comprising a soluble portion having a molecular weight distribution (Mw/Mn) of 4.57 and propylene content of 20.6 mol %, and an insoluble portion having a molecular weight distribution of 3.04 and propylene content of 2.9 mol %.
Japanese Patent Application Kokai No. 60-35007 describes a process for polymerizing ethylene either alone or together with an .alpha.-olefin having at least 3 carbon atoms under the presence of a catalyst containing a metallocene and a cyclic alumoxane represented by the formula: ##STR5## wherein R is a C.sub.1-5 alkyl radical and n is an integer of 1 to about 20, or a linear alumoxane represented by the formula: ##STR6## wherein R and n are as described above. The polymer prepared by such a process has a weight average molecular weight of about 500 to about 1,400,000 and a molecular-weight distribution of 1.5 to 4.0.
Japanese Patent Application Kokai No. 60-35008 discloses that a polyethylene or an ethylene-C.sub.3-10 .alpha.-olefin copolymer having a wide molecular-weight distribution may be prepared by using a catalyst system containing at least two metallocenes and an aluminoxane. There is also disclosed that said copolymer has a molecular-weight distribution (Mw/Mn) of 2 to 50.
The catalysts comprising a transition metal compound and an aluminoxane as proposed in the above-mentioned patent applications are provided with a significantly superior polymerization activity compared to the conventional catalyst systems prepared from a transition metal compound and an organoaluminum compound. These catalysts, however, are mostly soluble in the reaction system, and frequently require adoption of solution polymerization system.
On the other hand, attempts have been made to polymerize an olefin in dispersion or gas-phase polymerization systems by using catalysts wherein one or both of said transition metal compound and said aluminoxane are supported on a porous carrier of an inorganic oxide such as silica, silica-alumina, and alumina.
For example, aforementioned Japanese Patent Application Kokai Nos. 60-35006, 60-35007 and 60-35008 disclose that the transition metal compound and the aluminoxane supported on a carrier such as silica, silica-alumina, and alumina can also be used as catalysts.
Japanese Patent Application Kokai Nos. 60-106808 and 60-106809 disclose a process for preparing a composition comprising a polyethylene-based polymer and a filler which involves preliminarily contacting a high-activity catalyst component containing titanium and/or zirconium which is soluble in a hydrocarbon solvent with a filler, and then polymerizing ethylene or copolymerizing ethylene and an .alpha.-olefin under the presence of the thus treated catalyst component, an organoaluminum compound, and a filler which has an affinity for a polyolefin.
Japanese Patent Application Kokai No. 61-31404 discloses a process for polymerizing ethylene or copolymerizing ethylene and an .alpha.-olefin under the presence of a mixed catalyst comprising a transition metal compound and a product obtained by reacting a trialkylaluminum and water under the presence of silicon dioxide or aluminum oxide.
Japanese Patent Application Kokai No. 61-276805 discloses a process for polymerizing an olefin under the presence of a catalyst comprising a reaction mixture between an inorganic oxide containing surface hydroxyl radical such as silica and a reaction mixture obtained by reacting a zirconium compound and an aluminoxane with a trialkylaluminum.
Japanese Patent Application Kokai Nos. 61-108610 and 61-296008 disclose a process for polymerizing an olefin under the presence of a catalyst comprising a transition metal compound such as a metallocene and an aluminoxane supported on a carrier such as an inorganic oxide.
However, when an olefin is polymerized or copolymerized in a dispersion or gas-phase polymerization system by utilizing the carrier-supported solid catalyst components as mentioned above, polymerization activity is markedly reduced and the properties inherent to the catalyst comprising the transition metal compound catalyst component and the aluminoxane catalyst component are not fully exerted. Powder properties such as bulk density of the thus prepared polymer were also insufficient. Moreover, the above-mentioned catalysts are attended by a practical problem that a large amount of expensive aluminoxane was required to achieve high polymerization activity, and the polymerization activity was low when a small amount of aluminoxane was used.
It has been found that an adoption of a particular carrier-supported solid catalyst component may enable a production of catalysts having a high polymerization activity even when a smaller amount of the expensive aluminoxane is used in the catalyst. It has also been found that such catalysts are capable of producing an olefin polymer having excellent powder properties and narrow molecular-weight distribution or an olefin copolymer having both narrow molecular-weight distribution and composition distribution when applied to a copolymerization of two or more olefins, and particularly, ethylene polymer or an ethylene-.alpha.-olefin copolymer having excellent powder properties and narrow molecular-weight/composition distribution.